This invention relates generally to machining, and in particular to laser machining techniques for precision parts manufacture. Specifically, the invention concerns optical detection and control systems for laser cutting, laser drilling, etching, coating removal and other laser-based manufacturing processes.
Laser drilling and laser machining are forms of laser ablation, in which material is removed from a body by heating it with a laser so that it undergoes a chemical or physical phase change, for example by burning or melting. Depending upon the wavelength, beam intensity and workpiece composition, the phase change can also involve evaporation, sublimation, or, at higher intensities, plasma formation.
In surface machining applications, ablation occurs primarily within a relatively small distance of the surface, for example to form patterns, rough surfaces and other textures. Surface machining techniques also include engraving characters and symbols, forming or removing surface coatings, and laser ablation cleaning.
In other techniques the machining depth is greater, and ablation is not limited to the working surface. In laser cutting and laser drilling, for example, material is also removed from beneath the surface to form slots, holes, channels and other more complex features. Depending upon application, such features are either formed to a particular depth, or penetrate through the workpiece. Laser techniques can also be used to remove larger sections of material, for example by cutting a single workpiece into two or more parts.
Laser machining is performed at wavelengths ranging from the infrared and microwave to the ultraviolet and beyond, utilizing both pulsed-beam and continuous-wave technologies. In pulsed-beam systems, the pulse width typically ranges from a few femtoseconds to many milliseconds or more, and pulse timing can be precisely controlled in order to form detailed features with reduced heating of the surrounding workpiece. Continuous-wave devices are typically used for laser cutting and other high-intensity applications, but the beam energy can also be modulated in order to reduce the intensity for engraving, surface texturing and other non-breakthrough processes.